1. Field of the Invention
The present invention relates to hand held image based ID code readers and more particularly to an assembly that includes a single imaging module that can be used with any of several different power/communication modules so that the imaging module can be used in any of several different applications.
2. Description of the Related Art
Images acquired for code reading, also known as direct part mark (“DPM”) or label-based identification, include one or more 1D (e.g., a barcode) or 2D (e.g., a Data Matrix code) symbols located on an object. The code reading process includes repeatedly introducing an object marked with either 1D or 2D codes within a field of view of an image acquisition sensor (e.g., CMOS camera, CCD, etc.), illuminating the codes, and acquiring images, i.e., image data, containing the codes. Each code contains a set of predetermined patterns from which an attached data processor, such as a computer, can derive useful information about the object (e.g., serial number, type, model, price, etc.).
The handheld ID code reader can be connected to a server or remote processor via a network to exchange code reading results, images, as well as reader setup and reader status information. This connection can be facilitated via several different interfaces. For instance, exemplary interface options include a tether which includes a cable and a power source or a wireless interface that uses RF for data transition and energy storage devices (e.g., rechargeable batteries) as a power source. When a reader is to be used generally in one area, a tethered interface may be employed and, where an interface is to be used in many different and disperse locations, a wireless interface may be employed.
In addition to requiring either wireless or tethered interfaces, different systems often require different communication protocols and reader interfaces. For instance, some systems may require a reader to communicate via any one of RS232, Bluetooth, USB, PS2, Ethernet, RS485, etc. Here, if a reader includes an RS232 interface, that reader cannot be used with a system that communicates via one of the other interface types (e.g., USB, Ethernet, etc.). Thus, if a facility installs a new system that communicates via USB or some other interface type, the RS232 reader could not be used in the new system. Similarly, if a reader is configured to communicate via a tether and Ethernet and a facility upgrades the communication system to wireless Bluetooth, the reader cannot be used with the new system.
One solution to the above problem would be to provide a reader that is equipped to communicate via any of the possible types of interfaces. While this solution would provide a versatile reader, there are several shortcomings to this solution. First, with respect to Ergonomics, having a high number of interfaces requires a reader to have a connector with a high number of contacts. A multi-interface connector can only reasonably be placed at the bottom side of a reader handle. More contacts increase the size of the connector and the handle size/diameter. Due to ergonomic constraints there is a limit on handle size. In addition, more interface contacts would require more wires inside a tethered cable resulting in higher cable weight and lower flexibility making it difficult to easily move the reader. Moreover, for the majority of practical applications, only one interface is desired at a time.
With respect to power requirements, the intention of a wireless reader with RF communication is that it operates without any cables. This requires a battery to power the device. Because of the relative high power consumption of an image based ID reader the operating time is limited by the battery capacity. This makes it necessary to have a rechargeable battery. A typical interface for a tethered ID readers is RS232, which allows exchanging data serially. RS232 cannot power a device and some kind of external power supply (e.g. wall adapter) is necessary to power the reader. In contrast, other interfaces like PS2, USB and Ethernet (Power Over Ethernet (POE)) are capable of providing enough power for an attached reader. Some protocols, especially USB and POE have complex power management requirements like start-up current limitations, power sequencing and classification, and low power mode. An extremely complex interface assembly would be required to support all of the possible communication protocols currently in use.
With respect to electronics for each of the interface types, different interface types communicate using different signal levels and have different requirements in terms of signal speed and quality. Multiplexing different interface signals to a limited number of connector pins would require a huge technical effort and is not practicable in a cost and size reasonable way. In addition, electronic parts could be damaged if an error occurs and a multiplexer is set to a wrong connection type. Moreover, all contacts with external connections must be protected against electro static discharge (ESD). Because of the different signal levels and high speed requirements associated with different interface types, a one for all protection circuit is not optimal for all interface types.